US7443611B2ExpiredUtilityA1

Imaging lens

86
Assignee: FUJINON CORPPriority: Jul 4, 2005Filed: Jun 30, 2006Granted: Oct 28, 2008
Est. expiryJul 4, 2025(expired)· nominal 20-yr term from priority
Inventors:Yoshikazu Shinohara
G02B 13/18G02B 9/34G02B 13/004
86
PatentIndex Score
16
Cited by
7
References
29
Claims

Abstract

An imaging lens is provided and includes: a first lens of a positive lens; a second lens of a negative lens whose concave surface faces to an image side of the second lens; a third lens of a positive lens, whose both surfaces are aspheric, having a concave surface facing to an object side of the third lens; and a fourth lens of a meniscus lens, whose both surfaces are aspheric, having a convex surface facing to the object side near the optical axis, the lenses being arranged in this order from an object side, the first imaging lens satisfying the conditional expressions specified in the specification.

Claims

exact text as granted — not AI-modified
1. An imaging lens comprising: in order from an object side of the imaging lens,
 a first lens of a positive lens; 
 a second lens of a negative lens having a concave surface on an image side thereof; 
 a third lens of a positive lens having a concave surface on an object side thereof, wherein both surfaces of the third lens are aspheric; and 
 a fourth lens of a meniscus lens having a convex surface on an object side thereof and near an optical axis, wherein both surfaces of the fourth lens are aspheric, 
 the imaging lens satisfying conditional expressions (1) to (6):
   0.3 <|f   1   /f   2 |<0.8  (1) 
   ν dG1 −ν dG2 >25  (2) 
   | A 1|<1.5×10 −5 ×1/° C.  (3) 
   | A 2|<1.5×10 −5 ×1/° C.  (4) 
   | A 3|>1.5×10 −5 ×1/° C.  (5) 
   | A 4|>1.5×10 −5 ×1/° C.  (6) 
 
 wherein 
 f 1  represents a focal length of the first lens, 
 f 2  represents a focal length of the second lens, 
 ν dG1  represents Abbe number of the first lens, 
 ν dG2  represents Abbe number of the second lens, 
 A 1  represents a linear coefficient of expansion of the first lens, 
 A 2  represents a linear coefficient of expansion of the second lens, 
 A 3  represents a linear coefficient of expansion of the third lens, and 
 A 4  represents a linear coefficient of expansion of the fourth lens. 
 
   
   
     2. The imaging lens according to  claim 1 , wherein both surfaces of the first lens are aspheric, and both surfaces of the second lens are spherical. 
   
   
     3. The imaging lens according to  claim 2 , wherein said spherical surfaces include a plane. 
   
   
     4. The imaging lens according to  claim 1 , wherein said third lens is a positive meniscus lens. 
   
   
     5. The imaging lens according to  claim 1 , further comprising a diaphragm arranged at the image side of said first lens. 
   
   
     6. The imaging lens according to  claim 1 , wherein said first lens and said second lens have a light convergence function and a color aberration correction function, and said third lens and said fourth lens have a function of correcting aberrations such as spherical aberration. 
   
   
     7. The imaging lens according to  claim 1 , wherein at least one of said first lens and said second lens is made of glass. 
   
   
     8. The imaging lens according to  claim 1 , wherein at least one of said third lens and said fourth lens is made of plastic. 
   
   
     9. The imaging lens according to  claim 1 , wherein said first lens and said second lens are made of a glass material whose refractive index and linear coefficient of expansion are small with a rise in temperature, to reduce variations in the focus position. 
   
   
     10. The imaging lens according to  claim 1 , wherein said first lens is a positive meniscus lens. 
   
   
     11. The imaging lens according to  claim 1 , wherein said second lens is a negative meniscus lens. 
   
   
     12. The imaging lens according to  claim 1 , wherein said first lens is a positive meniscus lens whose surface with a stronger curvature faces to the object side, and said second lens is a negative a meniscus lens whose surface with a weaker curvature faces to an object side. 
   
   
     13. The imaging lens according to  claim 1 , wherein
 said fourth lens is designed to have a positive curvature near the optical axis and a negative curvature near the optical axis on the surface facing to the object side, and 
 on the surface facing to the image side, the fourth lens is designed to show a similar change in the curvature sign. 
 
   
   
     14. The imaging lens according to  claim 1 , wherein said first lens and said second lens are bonded together. 
   
   
     15. The imaging lens according to  claim 14 , wherein a diaphragm is arranged to come into contact with the surface of said first lens facing to the object side. 
   
   
     16. An imaging lens comprising: in order from an object side of the imaging lens,
 a first lens of a positive lens made of a glass material; 
 a second lens of a negative lens made of a glass material and having a concave surface on an image side thereof; 
 a third lens of a positive lens made of a plastic material and having a concave surface on an object side thereof, wherein both surfaces of the third lens are aspheric; and 
 a fourth lens of a meniscus lens made of a plastic material and having a convex surface on an object side thereof and near an optical axis, wherein both surfaces of the fourth lens are aspheric, 
 the imaging lens satisfying conditional expressions (1) to (2):
   0.3 <|f   1   /f   2 |<0.8  (1) 
   ν dG1 −ν dG2 >25  (2) 
 
 wherein 
 f 1  represents a focal length of the first lens, 
 f 2  represents a focal length of the second lens, 
 ν dG1  represents Abbe number of the first lens, and 
 ν dG2  represents Abbe number of the second lens. 
 
   
   
     17. The imaging lens according to  claim 16 , wherein both surfaces of the first lens are spherical, and both surfaces of the second lens are spherical. 
   
   
     18. The imaging lens according to  claim 17 , wherein said spherical surfaces include a plane. 
   
   
     19. The imaging lens according to  claim 16 , wherein said third lens is a positive meniscus lens. 
   
   
     20. The imaging lens according to  claim 16 , further comprising a diaphragm arranged at the image side of said first lens. 
   
   
     21. The imaging lens according to  claim 16 , wherein said first lens and said second lens have a light convergence function and a color aberration correction function, and said third lens and said fourth lens have a function of correcting aberrations such as spherical aberration. 
   
   
     22. The imaging lens according to  claim 16 , wherein said first lens is a positive meniscus lens. 
   
   
     23. The imaging lens according to  claim 16 , wherein said second lens is a negative meniscus lens. 
   
   
     24. The imaging lens according to  claim 16 , wherein said first lens is a positive meniscus lens whose surface with a stronger curvature faces to the object side, and said second lens is a negative a meniscus lens whose surface with a weaker curvature faces to an object side. 
   
   
     25. The imaging lens according to  claim 16 , wherein
 said fourth lens is designed to have a positive curvature near the optical axis and a negative curvature near the optical axis on the surface facing to the object side, and 
 on the surface facing to the image side, the fourth lens is designed to show a similar change in the curvature sign. 
 
   
   
     26. The imaging lens according to  claim 16 , wherein said first lens and said second lens are bonded together. 
   
   
     27. The imaging lens according to  claim 26 , wherein a diaphragm is arranged to come into contact with the surface of said first lens facing to the object side. 
   
   
     28. An imaging lens comprising: in order from an object side of the imaging lens,
 a first lens of a positive lens; 
 a second lens of a negative lens having a concave surface on an image side thereof; 
 a third lens of a positive lens having a concave surface on an object side thereof, wherein both surfaces of the third lens are aspheric; and 
 a fourth lens of a meniscus lens having a convex surface on an object side thereof and near an optical axis, wherein both surfaces of the fourth lens are aspheric, 
 the imaging lens satisfying conditional expressions (1) and (2):
   0.3 <|f   1   /f   2 |<0.8  (1) 
   ν dG1 −ν dG2 >25  (2) 
 
 wherein 
 f 1  represents a focal length of the first lens, 
 f 2  represents a focal length of the second lens, 
 ν dG1  represents Abbe number of the first lens, 
 ν dG2  represents Abbe number of the second lens, and 
 wherein said first and second lenses have relatively small linear coefficients of expansion, and said third and fourth lenses have linear coefficients of expansion which are larger than the liner coefficients of expansion of said first and second lenses. 
 
   
   
     29. An imaging lens comprising: in order from an object side of the imaging lens,
 a first lens of a positive lens; 
 a second lens of a negative lens having a concave surface on an image side thereof; 
 a third lens of a positive lens having a concave surface on an object side thereof, wherein both surfaces of the third lens are aspheric; and 
 a fourth lens of a meniscus lens having a convex surface on an object side thereof and near an optical axis, wherein both surfaces of the fourth lens are aspheric, 
 the imaging lens satisfying conditional expressions (1) and (2):
   0.3 <|f   1   /f   2 |<0.8  (1) 
   ν dG1 −ν dG2 >25  (2) 
 
 wherein 
 f 1  represents a focal length of the first lens, 
 f 2  represents a focal length of the second lens, 
 ν dG1  represents Abbe number of the first lens, and 
 ν dG2  represents Abbe number of the second lens, and 
 wherein liner coefficients of expansion of said first and second lenses are smaller than linear coefficients of expansion of said third and fourth lenses.

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